Heat exchangers typically are single units, in which a regularly spaced plurality of generally parallel flow tubes carry a flow medium, such as refrigerant or radiator coolant, with air blown perpendicular to and over the outside of the flow tubes to transfer heat to or away from the tubes. Composite heat exchangers in which one heat exchanger is fixed in front of the other as a modular unit, such as a radiator dualed with a condenser, have been proposed. But these typically share no more components than is necessary to simply physically attach them together for simultaneous installation. Shell type, tube within concentric tube, heat exchangers are known, but these are typically liquid to liquid heat exchangers, and still constitute only a single unit, rather than first, independently operating heat exchanger surrounded or jacketed by a second.
There may be applications in the future requiring that a primary, inner heat exchanger be contained within and jacketed by, a secondary heat exchanger. The outer, surrounding heat exchanger could carry a secondary flow medium of differing properties from the primary medium. The primary heat exchange medium could be confined to an isolated location within its circuit, while the secondary heat exchange medium alone could flow back to a vehicle passenger space or the like, where it was desired not to expose the passenger space to the primary heat exchange medium. The two heat exchange media would be thermally conductive, but not physically mixed. Patented methods exist for producing inner tubing jacketed by an outer, surrounding tubing, and it is suggested that such could be used for a heat exchanger. However, there is no design known for practically and compactly jacketing a primary heat exchanger within a secondary heat exchanger.